So, last semester I played League of Legends for about 3 hours average every day (that includes weekends, people)

I like LoL, but I want another game too. I have some money and I was looking at buying a game that might be fun and entertaining both in multiplayer and single player. Basically either an FPS or an RTS. Thing is, I don't really know what I want and there seem to be an appaling lack of demos out there for some of the games that sound interesting. I tried World in Conflict today and it didn't seem like my cup of tea, I think Battlefield: Bad Company II might be interesting, but there is no PC demo for it so I'm at a loss to know how good it is.

So, any suggestions for a good RTS or FPS game for the PC? And no, CoD Blac Ops doesn't count. Plus its about twice as expensive as I'd like to pay. I'd really like it if I could keep my costs to 30 dollars.